I had my dist directory included in my .gitignore file so I was not committing dist to my repo and not pushing it to Heroku. Therefore, Heroku could not find any content to serve.
I updated my .gitignore, committed, and pushed, and my app shows up just fine on Heroku now.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…